Four-character patterns (四字格)
语体 / register & style
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
Beyond fixed 成语, Chinese has productive four-character moulds you can fill in. Recognising them helps you parse expressions you've never seen:
• 不A不B: "neither too A nor too B" (不大不小) or "without A" (不知不觉, without realising).
• 半A半B: "half A, half B" (半信半疑, half-believing).
• 有A有B: "with both A and B" (有说有笑, chatting and laughing).
• 一A一B: one of each, often contrasting (一问一答, question and answer).
• 自A自B: "by oneself" (自言自语, talk to oneself).
• 东A西B: "here and there" (东张西望, look all around).
These give rhythm and elegance to writing, especially in art criticism and literature.
Examples
观众听得不知不觉入了迷。
Guānzhòng tīng de bù zhī bù jué rù le mí.The audience grew spellbound without even realising it.
对于这位画家的新作品，评论家们半信半疑。
Duìyú zhè wèi huàjiā de xīn zuòpǐn, pínglùnjiāmen bàn xìn bàn yí.Critics were half-convinced, half-doubtful about the painter's new work.
两位演员一唱一和，配合得非常默契。
Liǎng wèi yǎnyuán yí chàng yí hè, pèihé de fēicháng mòqì.The two performers echoed each other in perfect harmony.
老人坐在画前，自言自语地说着什么。
Lǎorén zuò zài huà qián, zì yán zì yǔ de shuō zhe shénme.The old man sat before the painting, muttering something to himself.
Common mistakes
✗ Mixing moulds: ✗ 半知不觉 → ✓ 不知不觉.
✗ Inventing any 四字格: combinations are partly fixed by usage; check before writing one.
✗ Reading 一唱一和 as *hé*: ✓ *hè* (to echo).